Karri Uotila

Bio: Karri Uotila is an academic researcher from Natural Resources Institute Finland. The author has contributed to research in topics: Picea abies & Thinning. The author has an hindex of 5, co-authored 7 publications receiving 90 citations.

Effect of soil preparation method on economic result of Norway spruce regeneration chain

Abstract: Economic result of forest regeneration chains, based either on spot mounding or on disc trenching and planting of Norway spruce (Picea abies [L.] Karst.) seedlings, were clarified and compared to each other. First, effects of soil preparation method on early development of Norway spruce stands were measured from field experiments. Second, the effects of soil preparation method on stand level management programs were modelled. The modelling was based on growth simulation and investment calculations. The soil preparation methods substantially affected early development of a stand. The density of the removed trees in early cleaning was 56% higher on the disc-trenched area compared to the spot-mounded area. The difference was especially high (120%), close by (<25 cm) the remained spruce seedlings. There was also a difference between the methods in the growth of crop spruces; at biological age of 8 years, the mean height of spruce was 110 cm on the spot-mounded area and 68 cm on the disc-trenched area. The differences led to divergent management programs between the areas. The disc-trenched area needed three young stand management operations whereas two was enough at the spot-mounded area. Although disc trenching is a less expensive method than spot mounding, the total management costs were higher in disc trenching than in spot mounding. Furthermore, incomes from the first commercial thinning were higher when regeneration based on spot mounding. At the interest rate of 3%, the investment in spot mounding had 329 € ha –1 higher net present value than the investment in disc trenching.

Estimating the need for early cleaning in Norway spruce plantations in Finland

Abstract: Effective management of Norway spruce (Picea abies (L.) Karst.) plantations requires detailed information on stand development, which is costly to measure. However, estimating the need for early stand management from site attributes that persists stabile after ones measured, may provide an inexpensive alternative. This study compared hardwood competition in spruce plantations of varying ages and tested the usability of this information in estimating the need for early cleaning. The data included 197 spruce plantations (4–7 years old) inventoried in southern Finland in 2007. The level (Low, Substantial, High) of need for early cleaning was subjectively determined by contrasting location and size of competing hardwoods to a conifer crop tree. Then the stage of the need for early cleaning was modelled according to site and stand attributes. Nearly 60% of the conifer crop trees in the plantations were subjectively judged to require early cleaning (Substantial 37.2%, High 21.2%), but only 10 per cent of the evaluated area was cleaned. Need for cleaning was intense on peatlands or damp soils, whereas it was mild on unprepared soils or cleaned sites. Traditional site characteristics used in forest management planning can be useful for recognising the peripheral cases, where need for cleaning is probably high or low. However, on a typical mineral soil plantation (uncleaned, soil prepared) the model indicates the differences in the need for early cleaning weakly. The need for early cleaning was already high in 4-year-old plantations, why stand age did not have significant effect on development of the need. Thus, the timing of an operation can not be predicted with the model. Nonetheless, early cleaning very likely opens growth space of crop trees in a 4–7-year-old spruce plantation. Therefore, from an aspect of crop growth, an uncleaned Norway spruce plantation in this age group is quite consistently worth cleaning.

Labour consumption models applied to motor-manual pre-commercial thinning in Finland

Abstract: Highlights •� When a young stand grows and gets older, the work time needed to make pre-commercial thinning increases. The stands of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and hardwoods (Betula spp.) required an additional 8.2%, 5.2%, and 3.3% work-time per year, respectively. Abstract Labour models were developed to estimate the time required to Pre-Commercially Thin (PCT) with a clearing saw 4- to 20-year-old stands of the main commercial tree species in Finland. Labour (i.e., work-time consumption) was estimated from the density and stem diameter of the removal of 448 stands via an existing work productivity function. The removal based estimator attainedwasusedasthebasisforapriorimixedlinearregressionmodels. �Themainfindingwas � that when a young stand grows and gets older, the work time needed to make a PCT increases. The stands of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and hard- woods (Betula spp.) required an additional 8.2%, 5.2%, and 3.3% work-time per year, respectively. Site fertility also played a role in that the most fertile site (mesic OMT) had an estimated labour requirement 114% higher than that for dryish VT. We also note that, per unit area, small stands require less labour than large ones and soil preparation method had a minor effect on the labour estimate. The stands which had previously gone through PCT were separately analysed. In those stands,�theonlysignificantvaria bleconcerningthelabourestima tewasage. �Theapriorimodels � described here can help foresters to develop economic management programmes and issue quotes for forestry services.

Kustannustehokas ja kannattava metsänuudistamisketju

Abstract: Sanotaan, että hyvää ei saa halvalla. Metsänuudistamisessakin yksittäisessä toimenpiteessä halvimman vaihtoehdon valinta voi myöhemmissä toimenpiteissä johtaa moninkertaisiin kustannuksiin. Yksi esimerkki tästä on maanmuokkaus, jossa säästetyt eurot menetetään yleensä moninkertaisesti jo taimikonhoitovaiheessa. Metsänuudistamisen kustannuksia, kustannustehokkuutta ja kannattavuutta tuleekin tarkastella koko uudistamisketjun näkökulmasta. Kannattavuus ratkaistaan pitkälti metsänhoidon menetelmävalinnoilla ja töiden ajoituksella. Uudistamisketjussa valintoja tehdään muun muassa uudistamistavan, taimitai siemenmate riaalin, maanmuokkausmenetelmän sekä kilpailevan kasvillisuuden torjuntamenetelmien ja taimikonhoidon ajoituksen suhteen. Uudistamisketjun menetelmävalinnat ovat vahvasti toisistaan riippuvaisia. Aiemmat toimenpiteet vaikuttavat ketjun myöhempien toimenpiteiden valintaan, ajoitukseen ja kustannuksiin. Uudistamisketjun alkupisteestä voidaan ajatella lähtevän useita vaihtoehtoisia polkuja, joista kukin haarautuu taas seuraavan toimenpiteen kohdalla. Vaihtoehtoisia uudistamisketjuja on siis useita erilaisia. Uudistamisen kokonaiskannattavuutta voidaan arvioida vasta polkujen päätepisteissä. Yleensä uudistamisketjun katsotaan päättyvän metsikön ensiharvennukseen. Useampikin polku voi johtaa kannattavuudeltaan lähes samaan lopputulokseen. Vaikka uudistamisketjua analysoitaessa havaittavat pienet kannattavuuserot hukkuvatkin helposti ennustemallien epävarmuuteen, voidaan tärkeimmät suuntaviivat kuitenkin osoittaa luotettavasti jo maanmuokkausta suunniteltaessa.

Mechanical site preparation for forest restoration

Abstract: Forest restoration projects have become increasingly common around the world and planting trees is almost always a key component. Low seedling survival and growth may result in restoration failures and various mechanical site preparation techniques for treatment of soils and vegetation are important tools used to help counteract this. In this article, we synthesize the current state-of-knowledge concerning mechanical site preparation for improved tree establishment when carried out in different forest restoration situations, point out critical research gaps and provide some recommendations for future directions. Mechanical site preparation often results in improved seedling survival and growth. However, if not intensive methods with much soil disturbance are used, it is a rather ineffective tool for controlling competing vegetation. Methods such as scarification, mounding and subsoiling also lead to multiple interactions among soil physical and chemical properties that affect plant survival and growth, and it may be difficult to determine the actual cause–effect relationship of any positive seedling responses. Most research to date on mechanical site preparation and plantation performance has been conducted using a few conifer tree species. Seedling responses differ among tree species and alternative species are often used during restoration compared to production forestry indicating a need for additional research for improved understanding. Several management objectives such as soil protection and increased biodiversity are many times relevant during forest restoration, and mechanical site preparation methods should be implemented carefully because they can have large impacts on the environment.

Use of UAV Photogrammetric Data for Estimation of Biophysical Properties in Forest Stands Under Regeneration

Abstract: The objective of this study was to assess the use of unmanned aerial vehicle (UAV) data for modelling tree density and canopy height in young boreal forests stands. The use of UAV data for such tasks can be beneficial thanks to the high resolution and reduction of the time spent in the field. This study included 29 forest stands, within which 580 clustered plots were measured in the field. An area-based approach was adopted to which random forest models were fitted using the plot data and the corresponding UAV data and then applied and validated at plot and stand level. The results were compared to those of models based on airborne laser scanning (ALS) data and those from a traditional field-assessment. The models based on UAV data showed the smallest stand-level R M S E values for mean height (0.56 m) and tree density (1175 trees ha−1). The R M S E of the tree density using UAV data was 50% smaller than what was obtained using ALS data (2355 trees ha−1). Overall, this study highlighted that the use of UAVs for the inventory of forest stands under regeneration can be beneficial both because of the high accuracy of the derived data analytics and the time saving compared to traditional field assessments.

Influence of mechanical site preparation on regeneration success of planted conifers in clearcuts in Fennoscandia-a review

Abstract: In the Nordic countries Finland. Norway and Sweden, the most common regeneration method is planting after clearcutting and, often, mechanical site preparation (MSP). The main focus of this study is to review quantitative effects that have been reported for the five main MSP methods in terms of survival and growth of manually planted coniferous seedlings of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and lodgepole pine (Pinus contorta var. latifolia Engelm.) in clearcuts in these three countries. Meta analyses are used to compare the effects of MSP methods to control areas where there was no MSP and identify any relationships with temperature sum and number of years after planting. In addition, the area of disturbed soil surface and the emergence of naturally regenerated seedlings are evaluated. The MSP methods considered are patch scarification, disc trenching, mounding, soil inversion and ploughing. Studies performed at sites with predominately mineral soils (with an organic topsoil no thicker than 0.30 m), in boreal, nemo-boreal and nemoral vegetation zones in the three Fenno-Scandinavian countries are included in the review. Data from 26 experimental and five survey studies in total were compiled and evaluated. The results show that survival rates of planted conifers at sites where seedlings are not strongly affected by pine weevil (Hylobius abietis L.) are generally 80-90% after MSP, and 15-20 percent units higher than after planting in non-prepared sites. The experimental data indicated that soil inversion and potentially ploughing (few studies) give marginally greater rates than the other methods in this respect. The effects of MSP on survival seem to be independent of the temperature sum. Below 800 degree days, however, the reported survival rates are more variable. MSP generally results in trees 10-25% taller 10-15 years after planting compared to no MSP. The strength of the growth effect appears to be inversely related to the temperature sum. The compiled data may assist in the design, evaluation and comparison of possible regeneration chains, i.e. analyses of the efficiency and cost-effectiveness of multiple combinations of reforestation measures.